Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$171.88	4.592%	$179.7727	$179.77	$179.75	$179.80
Purchase #2	$82.94	8.710%	$90.1641	$90.16	$90.15	$90.20
Purchase #3	$161.73	3.525%	$167.431	$167.43	$167.45	$167.40
Purchase #4	$127.84	3.712%	$132.5854	$132.59	$132.60	$132.60
Purchase #5	$227.51	10.682%	$251.8126	$251.81	$251.80	$251.80
Purchase #6	$82.68	10.379%	$91.2614	$91.26	$91.25	$91.30
Purchase #7	$98.78	3.140%	$101.8817	$101.88	$101.90	$101.90
7 purchase totals =	$953.36		$1,014.9089	$1,014.90	$1,014.90	$1,015.00